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Mon, 07 Sep 2026 08:12:14 -0700 (PDT) Date: Mon, 7 Sep 2026 17:12:13 +0200 From: Lorenzo Bianconi To: Eric Dumazet Cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Andrew Lunn , Ido Schimmel , Kuniyuki Iwashima , Artem Lytkin , netdev@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH net-next 3/9] ip_tunnel: use WRITE_ONCE in ip_tunnel_encap_setup Message-ID: References: <20260907075846.2913645-1-edumazet@google.com> <20260907075846.2913645-4-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="kwHWy4Oslr/sHH9R" Content-Disposition: inline In-Reply-To: <20260907075846.2913645-4-edumazet@google.com> X-Proofpoint-ORIG-GUID: RZk1zqNdUzjDb3O79nWBlvCM-AZacsAV X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA3MDE2OSBTYWx0ZWRfX8jYsL3dt7RYU NOLNkfbucketv5BA+F9HimV8EWDOj0hRktEDTWVndjEllu2sH5AOXh1Ve3JjRTJNsMsEmZ8AVFi RjbXrAgTEKwWHer3FOB8U5CgcjHik48tc4d9PQXkXnozCb+bvbsL0nvmnrkFQhjdFf04bvte0nD aeD8lcLZ+8NKHLbXNlEjPewI+DRxKgkZjL3GJFnxVOqhkttN5J7ThYFpBUaWdMZdZPmFurgE7KM gUEZHFCbILSoa1ADh5yUqYaz0tIWfNVUgWVRAJCW5PvMd/xrrd/Lj3wnIEzgbN5DmrTUYj5PR5/ TLE7kuWHcgBnjKGkvLdt17IZFio7lT5f5GdUL50Kq9l/zrWFE6SVAHqxNj1Lh0oPIKuQjSd4XGF e935l7ZI+llTOmt3rmWgQSEvPEXs1U70rnzL99JGUYg0RgtOQizJVP1C1lBH2AIlwg937hbXgDd 62lqM4EnThQBm1ucjGQ== X-Proofpoint-GUID: RZk1zqNdUzjDb3O79nWBlvCM-AZacsAV X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA3MDE2OSBTYWx0ZWRfX3hw1+LwiONAz qThs+cGty2qOhw7qkLxeB3QrwK5f0dZTgtfcXzscbF5vS+MkBRLynoLyVCKMPBty7F8S9lgPOTV 91SHSI4BGcjP+PsbBFRxVfYF5tOSo7A= X-Authority-Analysis: v=2.4 cv=AduB2XXG c=1 sm=1 tr=0 ts=6a9ed456 cx=c_pps a=ULNsgckmlI/WJG3HAyAuOQ==:117 a=WpTaRW6qxYHRGzLzQsVYzg==:17 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=1XWaLZrsAAAA:8 a=EUspDBNiAAAA:8 a=f6_07Eijtlnzn1mTpbQA:9 a=CjuIK1q_8ugA:10 a=h5nB1vRh8GYPN8VtIYEA:9 a=1WsBpfsz9X-RYQiigVTh:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-07_04,2026-09-07_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 adultscore=0 phishscore=0 clxscore=1015 suspectscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609070169 --kwHWy4Oslr/sHH9R Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable > Update ip_tunnel_encap_setup() to use WRITE_ONCE() when writing > to encap fields (type, sport, dport, flags) and hlen fields. > This ensures that concurrent lockless readers (like fill_info) > do not see torn writes. >=20 > Also remove the unsafe memset() on t->encap which could cause > concurrent readers to transiently see zeroed fields. > Removing it also fixes a bug where t->encap was left cleared > even if ip_encap_hlen() failed, resulting in partial configuration. >=20 > Fixes: 56328486539d ("net: Changes to ip_tunnel to support foo-over-udp e= ncapsulation") > Signed-off-by: Eric Dumazet Acked-by: Lorenzo Bianconi > --- > net/ipv4/ip_tunnel.c | 14 ++++++-------- > 1 file changed, 6 insertions(+), 8 deletions(-) >=20 > diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c > index e6bcf01411d0bcd12cc9a88e449d9283c4a83c64..13b5e35e8790b13ed4c87f28d= 46aa2bafc9ad72c 100644 > --- a/net/ipv4/ip_tunnel.c > +++ b/net/ipv4/ip_tunnel.c > @@ -491,19 +491,17 @@ int ip_tunnel_encap_setup(struct ip_tunnel *t, > { > int hlen; > =20 > - memset(&t->encap, 0, sizeof(t->encap)); > - > hlen =3D ip_encap_hlen(ipencap); > if (hlen < 0) > return hlen; > =20 > - t->encap.type =3D ipencap->type; > - t->encap.sport =3D ipencap->sport; > - t->encap.dport =3D ipencap->dport; > - t->encap.flags =3D ipencap->flags; > + WRITE_ONCE(t->encap.type, ipencap->type); > + WRITE_ONCE(t->encap.sport, ipencap->sport); > + WRITE_ONCE(t->encap.dport, ipencap->dport); > + WRITE_ONCE(t->encap.flags, ipencap->flags); > =20 > - t->encap_hlen =3D hlen; > - t->hlen =3D t->encap_hlen + t->tun_hlen; > + WRITE_ONCE(t->encap_hlen, hlen); > + WRITE_ONCE(t->hlen, hlen + t->tun_hlen); > =20 > return 0; > } > --=20 > 2.55.0.979.g7e5102b832-goog >=20 --kwHWy4Oslr/sHH9R Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTquNwa3Txd3rGGn7Y6cBh0uS2trAUCap7UTQAKCRA6cBh0uS2t rN92AQDM7fHzvbLLgghuBWHvpF8QW4Jb7mnSLoWitZ5vjubSjQD/dyjjNvoGj5oY N7qHDxw9W6nh0t9IjN+ZGxUqVQ1pwQ4= =ztjR -----END PGP SIGNATURE----- --kwHWy4Oslr/sHH9R--